John Pirro and Michael P. Mayko

Updated 8:21 pm, Saturday, November 16, 2013

Adam Lanza is pictured in this undated image from 2005 in Newtown, Connecticut. Twenty-six people were shot dead, including twenty children, after a gunman identified as Adam Lanza opened fire at Sandy Hook Elementary School. Lanza also reportedly had committed suicide at the scene. A 28th person, believed to be Nancy Lanza, found dead in a house in town, was also believed to have been shot by Adam Lanza.
Photo: Kateleen Foy, Photo By Kateleen Foy/Getty Imag

Adam Lanza is pictured in this undated image from 2005 in Newtown,...

MIAMI, FL - DECEMBER 18: In this photo illustration a Rock River Arms AR-15 rifle is seen on December 18, 2012 in Miami, Florida. The weapon is similar in style to the Bushmaster AR-15 rifle that was used during a massacre at an elementary school in Newtown, Connecticut. Firearm sales have surged recently as speculation of stricter gun laws and a re-instatement of the assault weapons ban following the mass shooting.
Photo: Joe Raedle, Getty Images

MIAMI, FL - DECEMBER 18: In this photo illustration a Rock River...

Nancy Lanza
Photo: Contributed Photo

Nancy Lanza

An undated photo of Nancy Lanza was provided by a family member.
Photo: Contributed Photo, Courtesy Family Of Nancy Lanza

State Trooper Richard McDaniel wears a pin on the lapel of his uniform denoting his work as a first responder to the mass shooting at Sandy Hook Elementary School in Newtown, Conn.
Photo: Autumn Driscoll

State Trooper Richard McDaniel stands outside the Troop A barracks in Southbury, Conn. Friday, Nov. 15, 2013. State troopers from Southbury were some of the first responders to the mass shooting at Sandy Hook Elementary School in Newtown, Conn.
Photo: Autumn Driscoll

State Trooper Richard McDaniel wears a pin on the lapel of his uniform denoting his work as a first responder to the mass shooting at Sandy Hook Elementary School in Newtown, Conn.
Photo: Autumn Driscoll

State Trooper Richard McDaniel wears a pin on the lapel of his uniform denoting his work as a first responder to the mass shooting at Sandy Hook Elementary School in Newtown, Conn.
Photo: Autumn Driscoll

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The season's first snowfall was gone from the ground when Inspector John Mahoney arrived at the Troop A barracks in Southbury early Tuesday afternoon for a meeting with detectives from the State Police Western District Major Crime Squad.

In his hands were five thick manila envelopes, sealed shut, each holding a copy of the report that Mahoney's boss, Danbury State's Attorney Stephen J. Sedensky III, had been laboring over for months, long before the detectives had even completed their investigation into the Dec. 14, 2012 shootings at Newtown's Sandy Hook Elementary School, an investigation unprecedented in size and scope in state history.

Inside the low-slung, brown brick building overlooking Interstate 84, the tall, curly-haired inspector handed the envelopes to a detective for delivery to state police commander Col. Dan Stebbins and other department brass.

Sometime later this month, the contents of those envelopes are expected to be made public and distributed to media from around the world, who have been trying to ferret out details of the investigation since shortly after the first frantic 911 call was made from the school.

"There are not going to be any theories," one investigator said.

A draft of the 40-page report, which is expected to have hundreds of pages of appendices attached, was presented to family members of the victims at a meeting on Thursday. They were allowed 20 minutes to review its grim findings, but they were not allowed to keep it and were asked not to discuss it, relatives told Hearst Connecticut Newspapers.

Many of the questions reporters and the public have been asking for months will be answered, according to sources familiar with the report and law enforcement experts involved in other major investigations in the past.

But the biggest question -- motive -- will not be among them. We may never know what prompted Adam Lanza, an ultra-reclusive 20-year-old with an obsession for firearms, violent video games and a fixation on mass murders and those who perpetrated them, to kill his mother, then blast his way into the school he briefly attended as a child and systematically mow down 20 first-graders and six staff members before ending his own life.

"The `a-ha' moment won't get answered," said David Schroeder a former investigator and now assistant dean at the University of New Haven. "I don't think you can answer that ... even if you piece together a life post mortem."

Piece by piece

In the more than 11 months since that day, a number of possible motives have been advanced for the deadliest mass shooting at an elementary school in the nation's history.

Family members and others who have spoken to the media have suggested Lanza was seeking retribution for bullying he suffered when he attended Sandy Hook years earlier; he was angry with his mother, Nancy, 53, for thwarting his ambitions of enlisting in the military; he was upset that she was thinking about moving from their Yogananda Street home or was considering having him committed to a psychiatric facility.

But the report may not address any of that, said Peter Valentin, a retired state police detective who compiled hundreds of reports when he worked with the major crime squad.

"Motivation is way beyond us," said Valentin. "Nothing we ever encountered could make sense out of this situation. How can you envision any set of circumstances that would give a person rise to do something like this?"

The complete document is the work of hundreds of investigators, along with federal prosecutors who drafted search warrants and agents from the FBI; U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives; the Department of Homeland Security and U.S. Marshal's Service. There are also reports from area police, firefighters, emergency medical technicians and medical examiners who responded to the scene.

"This was a unique situation," said Robert Paquette, a retired Danbury police chief and FBI supervisor. "There was no scorecard, no game plan to conduct an investigation like this."

In addition to motivation, there won't be any recommendations and probably no conclusions.

"That's not the purpose of the report," said Peter Massey, a retired Hamden detective and now head of the undergraduate forensics program at UNH. "That's left up to the politicians, experts, commissions, committees and society."

Mental health questions

But there will be plenty of detail to feed discussions and draw inferences.

Questions of Lanza's mental health could be confirmed by medical, psychological or school records that are expected to be included in the report. Did he have Asperger's syndrome, a form of autism, as books found in his mother's bedroom suggest? Had he ever had any kind of counseling? Was he taking any medication?

Lanza's elementary years were marked by changes of schools and home-schooling by his mother before he enrolled at Newtown High School, where those who remember him described Lanza as being extremely withdrawn with few, if any, friends. He eventually left high school and earned a GED before attending Western Connecticut State University part-time, but never graduated.

When state police searched his home after the shooting, they found that Lanza had been compiling information about other mass murders, including Anders Breivik, a Norwegian man who shot and killed 77 people in 2011, most of them young people attending a summer camp, and corresponded over the Internet with at least one other person, a young man in South Carolina, who shared his interest.

Authorities interviewed the South Carolina man, but determined that Lanza had not discussed his plans to attack the school, according to an investigator.

The discovery led to speculation that Lanza, who spent hours playing video games in the basement of his home -- moving characters into position to kill animated opponents in Call of Duty, or across a scorched earth in Gears of War, or as a janitor on a rampage in Kindergarten Killers -- targeted the school in an effort to top Breivik's total.

Powerful digital evidence

Abe Baggili, a computer forensic specialist, professor at University of New Haven and one of the first people to determine that smartphones could track a person's movements, said the digital trail Lanza left behind would likely inform the report.

"Many of the reports describe how he was a computer genius and an avid video game player," Baggili said. "Do you know of any computer genius or avid video game expert who has just one system, one or two devices? I don't."

There is potential evidence in every electronic device he had, whether it be smartphones, game consoles, laptops, iPad, iPod, or USB sticks. Every device would be studied, he said.

"More than 80 percent of all cases have some sort of digital evidence associated with them," Baggili said. Baggili has published a method in which digital evidence can be extracted from iPhones via iTunes. Now he is directing a research project aimed at developing a psychological profile of people based on the words they used in messages found on their devices.

"Digital evidence is very powerful," he said. "You can determine what sites were visited, when they were visited, how often and how long they were visited. You can uncover what was stored or deleted on the computer. You could find who was contacted, how often and what was said."

So Baggili and others believe the report could include a history of Lanza's relevant website activity, online conversations and text messages.

Before leaving his house Dec. 14, Lanza tried to destroy the hard drive from his computer, but that doesn't mean information has not be recovered from it.

"Of course, it depends on how hard he hit it," Baggili said.

Even if the outside case was shattered, the information-containing platters, which resemble compact discs, may have been spared. If damaged, the platters could still be reconstructed and read with the right equipment, he said, noting the FBI and Defense Department have restored hard drives damaged in bomb blasts.

The Lanza arsenal

The report should also include information on the array of firearms, swords and 1,400 rounds of ammunition found in the Lanza home. All the weapons, including the Bushmaster semi-automatic rifle that Lanza used at the school and the Glock pistol with which he killed himself, were registered and owned by his mother, a gun enthusiast who encouraged his interest in shooting.

Investigators have been tracing the weapons used, where they were made, where they were purchased and by whom, and compiling a history of Lanza's training on the weapons and his visits to shooting ranges with his mother, sources said.

Investigators were also reportedly intrigued by cellphone records indicating Lanza paid several visits to the Danbury Fair mall in spring 2012, months before the shooting, behavior they considered unusual since he rarely left home.

They obtained security videos from the mall in an attempt to determine whether he was meeting with anyone, but it's unknown at this point whether anything relevant to the investigation was found.

Police filled some two dozen large cardboard boxes with items removed from the home, at least a half-dozen containing documents and other paperwork, the remainder holding video games, controllers, computer accessories, weapons, ammunition and other objects they believed at the time could have a bearing on the case.

"A lot of the stuff had no value, but you take it because you don't know at the time if it might be valuable in the future," the investigator said. Those items will eventually be turned over to the executor of Nancy Lanza's estate.

A Sandy Hook pin

Perhaps the most heart-rending remnants from the long investigation are clothing worn by the victims when they died.

Troopers spent their own money to "launder and re-launder" them, removing bloodstains before packaging them up in case the families wanted them back, the investigator said.

Many did, but about a half-dozen sets of clothes remain unclaimed and will go into storage with the other evidence, should those families eventually change their minds, he said.

Symbolizing the end of the long investigation, Stebbins and a number of other high-ranking state police commanders went to the Southbury barracks on Wednesday to present the first of the specially-designed Sandy Hook pins to the more than 260 state police officers, nearly one-quarter of the state police force, who were involved in the investigation.

The enamel pin, a solid bar bearing the now-familiar green and white Sandy Hook school colors, is worn on the trooper's breast pocket -- a somber coda to a long investigation.